The HM7B is a European

cryogenic In physics, cryogenics is the production and behaviour of materials at very low temperatures. The 13th IIR International Congress of Refrigeration (held in Washington DC in 1971) endorsed a universal definition of “cryogenics” and “cr ...

upper stage A multistage rocket or step rocket is a launch vehicle that uses two or more rocket ''stages'', each of which contains its own engines and propellant. A ''tandem'' or ''serial'' stage is mounted on top of another stage; a ''parallel'' stage is ...

rocket engine A rocket engine uses stored rocket propellants as the reaction mass for forming a high-speed propulsive jet of fluid, usually high-temperature gas. Rocket engines are reaction engines, producing thrust by ejecting mass rearward, in accorda ...

used on the vehicles in the Ariane rocket family. It will be replaced by Vinci, which will act as the new upper stage engine on Ariane 6. Nearly 300 engines have been produced to date.

History

The development of HM7 engine begun in 1973 on a base of HM4 rocket engine. It was designed to power a third stage of newly constructed

Ariane 1 Ariane 1 was the first rocket in the Ariane family of expendable launch systems. It was developed and operated by the European Space Agency (ESA), which had been formed in 1973, the same year that development of the launcher had commenced. A ...

, the first launch system for

European Space Agency , owners = , headquarters = Paris, Île-de-France, France , coordinates = , spaceport = Guiana Space Centre , seal = File:ESA emblem seal.png , seal_size = 130px , image = Views in the Main Control Room (120 ...

. Maiden flight took place on 24 December 1979 successfully placing

CAT-1 CAT-1 (also Technological Capsule 1, also Obélix) was the first artificial Earth satellite launched by the European Space Agency , owners = , headquarters = Paris, Île-de-France, France , coordinates = , spaceport = Guiana ...

satellite on the orbit. With the later introduction of Ariane 2 and

Ariane 3 Ariane 3 was a European expendable carrier rocket, which was used for eleven launches between 1984 and 1989. It was a member of the Ariane family of rockets. The principal manufacturer for the Ariane 3 was Aérospatiale, while the lead agency ...

it became necessary to improve the performance of the upper stage engine. This was achieved by extending the nozzle length and increasing the chamber pressure from 30 to 35

bar Bar or BAR may refer to: Food and drink * Bar (establishment), selling alcoholic beverages * Candy bar * Chocolate bar Science and technology * Bar (river morphology), a deposit of sediment * Bar (tropical cyclone), a layer of cloud * Bar ( ...

, increasing the engine's

specific impulse Specific impulse (usually abbreviated ) is a measure of how efficiently a reaction mass engine (a rocket using propellant or a jet engine using fuel) creates thrust. For engines whose reaction mass is only the fuel they carry, specific impulse is ...

and resulting in a nominal burn time increase from 570 to 735 seconds. Qualification tests were completed in 1983 and this upgraded variant was designated HM7B. It was also used on the Ariane 4 vehicle's upper stage where the burn time was further increased to 780 seconds, and since 12 February 2005 it's also used on the upper stage of

Ariane 5 Ariane 5 is a European heavy-lift space launch vehicle developed and operated by Arianespace for the European Space Agency (ESA). It is launched from the Centre Spatial Guyanais (CSG) in French Guiana. It has been used to deliver payloads in ...

ECA.

Overview

The HM7B is a regeneratively cooled

gas generator A gas generator is a device for generating gas. A gas generator may create gas by a chemical reaction or from a solid or liquid source, when storing a pressurized gas is undesirable or impractical. The term often refers to a device that uses a ...

rocket engine fed with

liquid oxygen Liquid oxygen—abbreviated LOx, LOX or Lox in the aerospace, submarine and gas industries—is the liquid form of molecular oxygen. It was used as the oxidizer in the first liquid-fueled rocket invented in 1926 by Robert H. Goddard, an app ...

and

liquid hydrogen Liquid hydrogen (LH2 or LH2) is the liquid state of the element hydrogen. Hydrogen is found naturally in the molecular H2 form. To exist as a liquid, H2 must be cooled below its critical point of 33 K. However, for it to be in a fully l ...

. It has no restart capability: the engine is continuously fired for 950 seconds in its Ariane 5 version (780 s in the Ariane 4). It provides 62.7 kN of thrust with a

of 444.6 s. The engine's chamber pressure is 3.5 MPa.

References

{{Snecma aeroengines Spacecraft propulsion Rocket engines using hydrogen propellant Space program of France Rocket engines using the gas-generator cycle

History

Overview

See also

Comparable engines

References